Manufacture of extensible chains.



E. lBURKHAPJTI. MANUPAGTURB or BXTENSIBLB CHAINS.

APPLICATION FILED JULY 24, 1912.

Patented Dec. 17,1912.

' Tol all w'ltom it may concern.'

` provide means 'wherebyvthe individual main together.

` links in partly extended state.

4which I will term 'hereinafter outer and EMIL BUEKHnEDT, or PFORZHEIM,

l MANUEECTUEE or EXTEESIBLE CHAINS.

Specification of Letters Patent.

GERMANY.

Application led July 24, y1912. Serial No. 711,254. l

Be it known that I,.EM1L BURKHARDT. a subject ofthe German Emperor, and residing at Pforzheim, Germany, have invented certain new and useful Improvements in the Manufacture of lilxtensibley Chains, of which the following'is a specification. f

'Ihe present invention has reference to an improved method of making extensibleY chains, such asare used, for instance, in the manufacture of bracelets composed. of a4 series of concatenated, stretchable links, and the particular object of the invention is to links can be brazed at their joints prior to the introduction of the springs, so that the elasticity of the latter is not affected by the soldering heat.. j In order to' make this vinvention more readily understood, I will now describe it with reference to the accompanying drawing, in which-- Figures 1-7 show various, successi-ve stages of manufacture; Fig. 8 shows a'series. of interconnected links yin ordinary, contract'ed state; and Fig. 9 shows two such Each link is composed of twomem-bers,

inner-- members respectively. The 'outer' member is bent from a .suitably stamped andpressed blank aiv (Fig. 1) of two identical halves connected by areduced bridge b and provided at each free end with a` short lug. al.` The link halves vhave a profiled c'ross`- section and are provided near the ,bridge end with oppositely disposedfcut-o-uts c. rFliese blanks are bent to form a klink as shown in Fig. 2, the lugs d facing or over-v lapping each other. The inner links are closed 1n themselves,.as shown in Fig. 3and are provided at one .end at both sides with. small prongs or teeth f. They are hooked into the outer links through the still open lugs d, and the `latter are then hard soldered.v Next, the inner member is drawn into the fully extended position, shown in Fig. 4 in side elevation and in Fig. 5 in top view, and a helical spring g is inserted, and then the member is swung about inthe direction of the 'arrow 1, the soldered bridge serving as a pivot, until the side prongs f pass through the cut-outs c into the grooved interior of the outer member, when the two projecting lateral-,ly

members form ay casing for theentirely hidden spring. As Vthe shape of the prongs corresponds to the inner profile ofthe outer member, and as the inner links are guided also on the brazed bridge,` the two members can now move only in the direction of their longitudinal axis relative to one' another.

Patented Dem-17, 1912.

Into the projecting end of the inner member is then hooked the succeeding outer member,-'as shown in broken lines in Fig. `7, and

the fabove described operations are repeated. As' soon as such an inner member is linked int'otheneighboring outer member, it is effectively barred from jumping out of its own'main member,as it now cannot recede into the latter far enough for its prongs to pass through the cut-outs again.

The springs vtend to ordinarily hold the links in the position shown vin Fig. 8, but they the links, and allo,w of the inner ymembers sliding within Ithe/outer members to the desired extent. e K

- What I claim` is The method of making extensible chains which consists inl stamping or ressing a blank into the form of two identical halves connected by a bridge and provided at each free-end with a short lug, each half being grooved and'having oppositely disposed cutouts upon one side of each grooved portion, making other links rst named blank;y at the bridge portion -into U-shape and the lugs thereofinwardly until they nearly abut or overlap, inserting the closed link through the lugs into the space between the grooved portions of the other link, hard soldering the lugs together, drawsecond llink finto'a fully extended ing the e position, inserting a helical spring into readily yield` to longitudinal pull on' having'closed ends and provided near vone'end with prongs or teeth therefrom,-bending the the second linkswinging the latter about e the soldered lugs Auntil the prongs pass throughtheV cutI-'outs and vinto the grooved interior of thel first link, and similarly malngjand assembling or connecting other like links, substantially4 as described.

In 4testimony whereof I aix my signature in presence of two witnesses. I

. EMIL BURKHARDT.

. Witnesses:

' CARL ALT, y PAUL STEINEEV 

